Fingerprint sensors are key devices for automatic fingerprint acquisition. According to the principle of sensing, that is, the principle for fingerprint imaging, fingerprint sensors include optical fingerprint sensors, semiconductor capacitive sensors, semiconductor thermal sensors, ultrasonic sensors, and radio-frequency (RF) sensors, etc. The manufacturing for fingerprint sensors is comprehensive, and highly complicated and difficult.
The semiconductor capacitive sensors mainly utilize capacitors to acquire fingerprints. The semiconductor capacitive sensors demonstrate advantages including low price, small volume, high recognition rate, etc. and are commonly used in mobile phones, computers, cars, and home security identification systems.
In a semiconductor capacitive sensor includes a “plate” integrated with thousands of semiconductor devices, and a finger touching the “plate” may serve as an electrode of the capacitors. Because of the ridges and the valleys of the finger surface, the actual distances for the finger to make contact with the “plate” may be different at the ridge positions as compared to at the valley positions, resulting in different capacitance values at different positions of the fingerprint. The data at different positions are then collected to complete the acquisition of the fingerprint.
However, the sensitivity of the existing semiconductor fingerprint sensors still needs to be improved. The disclosed fingerprint sensors and fabrication methods thereof are directed to solve one or more problems set forth above and other problems in the art.